The present application relates to three-dimensional (3D) imaging systems that utilize a microlens array.
In 1908, Nobel Prize winning physicist Gabriel Lippmann proposed a technique that he called integral photography (IP), which can form 3D images using a two dimensional (2D) display, allowing the images to be observed with parallax and quasi-continuous viewing angles without needing any special viewing devices such as glasses to perceive 3D images. Integral photography uses a plane array or closely spaced small lenses to photograph a scene, recording images of the scene as it appears from many slightly different horizontal and vertical locations. When the resulting images are rectified and viewed through a similar array of lenses, a single integrated image, composed of small portions of all the images, may be seen by each eye. The position of the eye determines which parts of the small images it sees. Ideally, the visual geometry of the original scene may be reconstructed, so that the limits of the array seem to be the edges of a window through which the scene appears life-size and in three dimensions, realistically exhibiting parallax and perspective shift with any change in the position of the observer. While professor Lippmann's system used an array of tiny glass spheres, hemispherical lenses have also been used for IP.
The array of small lenses is sometimes called a microlens array (MLA). Another colloquial term is a fly's eye lens, so called because the insects have eyes with an array of small lenses. Individual lenses in the array are sometimes called lenslets. Each individual microlens in an array has the same size when used for IP, although there are other applications for which microlens sizes may vary. Microlens arrays having lenslets with circular, octagonal and square sides are known. Because the focusing portion of the lenslets have a circular outline, the octagonal sided array packs the most lenses in a given area and so is preferred over the square shape, which packs the least lenses in a given area. Typically, such microlenses have a spherical or semispherical curved focusing surface, although lenses with aspherical (e.g., parabolic) surfaces that are better at focusing light are known. Also, because human eyes are separated in a lateral direction, arrays of semi-cylindrical microlenses have been employed, which are easier to manufacture but offer 3D effects only in the lateral direction.
For the last several decades, research in this area has concentrated on the use of microlens arrays in combination with optoelectronic sensors and display devices. A recording device using a microlens array in combination with optoelectronic sensors is sometimes called a light field camera. The term integral imaging is often used for those systems that attempt to produce 3D images with these devices. Despite numerous advances, however, realistic 3D images have yet to be produced by integral imaging using these optoelectronic devices.